The ability to functionally test the effects of specific DNA sequences on developmental regulation (e.g. transcription and RNA processing) by gene transfer and analysis of modified genes in vivo provides a new dimension to the study of developmental regulation in metazoans. While the foundation of our understanding of genetic regulation comes from studies on prokaryotes and lower eukaryotes (e.g. fungi), the vast majority of these studies have examined the regulation of catalytic gene products (i.e. enzymes) in a variety of highly regulated metabolic pathways while genes studied in metazoans have been largely noncatalytic structural genes. The dopa decarboxylase (Ddc) and lambda (2)amd genes of Drosophila catechol metabolism are an ideal set of catalytic gene products in a single metabolic pathway that are amenable to genetic, developmental, and molecular analysis. Four specific questions are posed which will help us understand some general properties of developmental regulation. Is the expression of these metabolically related genes coordinated and, if so, how? What is the location and nature of the contiguous DNA encoded signals which govern control of developmental expression of these genes? What is the developmental significance of differential RNA processing in these genes? How are these genes organized in the genome and what is the functional or evolutionary significance of the organization? We have used transposon mediated gene transfer of cloned Ddc and amd DNA to rescue mutant embryos. In this study we will construct a series of gene fusions and specific alterations which can be functionally tested in vivo by transposon mediated transformation. These experiments will provide direct evidence for specific localization of regulatory signals controlling developmental expression of these catechol metabolizing enzymes.